In pursuit of studies on the regulation of protein synthesis in animal cells and the role of heme in cellular differentiation, we propose: (1) Study of the action of the heme-regulated eIF-2alpha kinase and of the dsRNA-activated eIF-2alpha kinase in normal animal and human reticulocytes and in blood cells of human pathologic conditions (iron-deficiency, sideroblastic anemia, plumbism, and viral infections). (2) Study of the role of phosphatases and of heat-stable phosphatase inhibitors in the regulation of the initiation of eukaryotic protein synthesis. (3) Further study of the effect of hemin on the differentiation of mouse 3T3 fibroblasts to adipocytes. (4) Study of the mechanism by which hemin promotes maturation and hemoglobinization in human K562 leukemic cells.